Regarding Draft-09... add an explicit statement that the server determines when and if the atom:updated element is modified
Whether or not to change atom:updated on an update request is implementation specific and can only reasonably be determined by the server. A server could choose to use the atom:updated value provided by the client, but is not required to do so.
8.6 Editing members and the atom:updated element Upon successfully processing an update request on a member resource or linked media resource, a server MAY modify the value of the members atom:updated element. The decision of whether or not to modify the value of atom:updated is an implementation choice that is dependent on whether or not the server considers the update to be significant.